We have one main domain and 4 sub domains running different instances and using same remote mysql database server. Some domains using PHP 5.6 and some using 5.5. we want to have our domains sharing the same PHP session, So that we can keep user data across these domains. I saw two methods Storing Sessions in a Database and using memcached. We are using redis on each servers.

Is it possible to set-up a centralised redis server to handle common php session across multiple servers